1. Field of the Invention
The present invention relates to an accumulating device for weft yarn feeders to textile machines, of the type comprising a fixed winding drum receiving windings of weft yarns, whose perpheral skirt is interrupted by openings housing so-called fingers or columns, essentially positioned parallel to the drum axis and actuated to swing in order to partially and variably project from said openings and cause said windings to advance on the drum keeping them spaced between each other. The columns, in sequence, radially move and longitudinally swing with respect to the drum due to the fact that they are connected to the feeder motor shaft through a series of coupling means.
2. Description of the Prior Art
As it is known, modern looms ensure constant operating cycles and regular sequence of the different manufacturing steps for every type of yarn. For these reasons the socalled shuttleless looms must be provided with weft feeders, in which the yarn is taken from a reel, is laid down in subsequent and parallel windings on a fixed drum and finally is taken from the latter in an axial direction to be fed to the loom, always ensuring, besides speed, also a constant tension to avoid sudden jerks which would cause process interruptions.
It is therefore necessary, for a regular manufacturing cycle, to always ensure a constant reserve of yarn on the drum.
Moreover it is sometimes necessary, for particular yarns, to warrant that said reserve be formed on the drum also by keeping a predetermined distance or step between each winding and the following one.
In order to comply with said requirement, various solutions have been proposed up to now. Among the most significant solutions we can mention the one of using so-called columns which are mounted in a non-rotary way within longitudinal grooves of the drum and are connected to the motor shaft of the feeder through a bearing and a rotary bush eccentric and sloping with respect to the shaft axis. When the latter rotates, the bush eccentricity and inclination cause on each column respectively a radial upward and downward movement and a longitudinal oscillation which, when combined, allow the column to lift the yarn windings from the drum surace, to advance them of one step and to lay them down again onto the drum surface. Said movement is performed in sequence by all columns, circularly to the drum, and the advancing step depends, eccentricity being equal, on the bush inclination with respect to the shaft.
This solution, though being valid, has the limitation of offering only a single value of the bush inclination and therefore a single value of the step between windings, which can be modified only by replacing the columns-bearingeccentric bush assembly with another one having an eccentric bush with a different inclination. It must be further notified that said inclination must be congruous with the direction of rotation of the motor shaft and when the latter changes it is practically necessary to replace the assembly.
Only said last replacement has been eliminated in the known technique (European patent application No. 0164033 published Dec. 11, 1985) by means of a bush in two pieces, which can be positioned at 180.degree. to one another in order to vary the direction of inclination according to the direction of rotation of motor shaft, on its turn depending on the yarn twisting, S or Z.
Another type of solution (European Patent application No. 0131313 published Jan. 16, 1985) consists in taking advantage of the filling of an elastic hollow body inside the drum in order to always ensure the progress of the windings as a consequence of the variations in elasticity of said hollow body. However said solution has the drawback of not ensuring a wide range of configurations of the elastic body and therefore it is not suitable for all corresponding types of yarns.